This invention relates to musical instruments, and more particularly to transducers for musical instruments which rely upon air pressure variations in the instrument to produce or enhance sound.
It is very often necessary to amplify the musical sound of instruments being played in a group, band or orchestra. To accomplish that, at least one microphone is placed in front to pick up the combined sound being produced. Most microphones exhibit a directivity pattern that allows picking up all of the instruments, but not all equally well. Wind instruments, such as saxophones and trumpets, are themselves highly directive. Consequently, unless the musician is in a position to play to the microphone, the sound system will fail to pick up the full quality of the tone. This is particularly critical in sound recording studios where only that which enters the microphone directly is to be recorded.
To overcome the problems of directive microphones and highly directive wind instruments, efforts have been made to use a pressure transducer of the monolithic integrated circuit type as nondirective microphones in woodwind instruments by one manufacturer of integrated circuits. The transducer itself was comprised of piezoresistors in a Wheatstone bridge prebiased by a reference cell and directly connected to a preamplifier. However, that type of transducer was only used to detect the envelope of pressure variations in a woodwind instrument for the sole purpose of modulating the risetime of the instrument's tones to emulate the "attack" of a brass instrument. A limiting microphone was reportedly coupled tightly to the instrument's bell to detect the frequency of the sounds at the output of the instrument, not their amplitudes. A modulator was then employed to modulate the frequency of the sounds with the envelope of the air pressure variations in the air column. It was not recognized that a pressure transducer in the air column of a wind instrument or drum could respond to high frequency, low amplitude variations in the air column, and thus pick up all musical sounds produced by the musician through the instrument.